Explore the chemical synthesis of a biofuel produced from algae and its comparisons with existing fuel sources
Bio-gasoline
Petroleum
Explore the chemical synthesis of a biofuel produced from agae and its comparison with existing fuel sources
Algal fuels are considered 'Third Generation' biofuels, developed to improve the viability of biomass derived fuels at large scale. Third generation fuels are derived from aquatic biomass, and therefore do not compete with traditional land based agriculture. Another advantage is reduced waste products due to lack of cellulose and fibrous materials. These fuels require more water than their predecessors, but can grow in high salinity environments, like the ocean.
(Brennan & Owende, 2010)
(Journal of Biotechnology and Bioengineering Research, 2024)
While third generation fuel sources can processed into ethanol, similarly to maize or sugar cane, their high oil and lipid content allows them to be refined into previously impractical fuel options.
Biogasoline is one of these, and is touted as a 'drop in replacement' for unleaded gasoline.
How do does the collection and cracking processes differ between synthesis of gasoline and biogasoline, and how do the final products
Is biogasoline produced from algae viable to synthesise, and a complete "drop in replacement" for gasoline.
Our current crude oil reserves are the result of organic matter pyrolysing underground over "millions of years" (Energy Education, n.d.-a).
Pyrolysis is the process of breaking down longer "heavy" hydrocarbon chains into smaller, "lighter" products in the absence of free oxygen molecules. In this case, the long molecules that make up the organic matter are broken down into more simple chains. Molecules not present in the shorter chains, such as oxygen, nitrogen, and hydrogen, form by-products such as
Oil is pumped from "wells", stored in, and sold by the barrel (Energy Education, n.d.-a).
While the product collected is heterogeneous, and contains a huge variety of unusable hydrocarbons, further pyrolysis under controlled conditions and in the presence of a catalyst permits controlled reformation of the crude product into useful and refined fuels. These products can then be separated through fractional distillation.
(U.S. Energy Information Administration, n.d.)
While natural cultivation was used initially due to its low capital cost, artificial cultivation is more viable for fuel production on industrial scale. Environmental conditions are controlled using closed loop systems and key consumables, notably

(Lumen Learning, n.d.)
As the algae grows and reproduces, carbon will accumulate in the system in the form of glucose, and within the oils that algae produce to store energy long term. The oils produced by certain species of algae contain high content of lipids; a portion of which are fatty acids. Fatty acids are long hydrocarbon chains with a carboxyl group at one end.
Harvested biomass is processed, and oils are extracted. The dried biomass then undergoes pyrolysis, which converts any remaining compounds into bio-oil, and similar by-products to crude oil (U.S. Department of Agriculture, n.d.).
Processing of algal/bio-oils is less efficient than crude oils. Since the main source of hydrocarbon chains is fatty acids, the carboxyl group adds a significant amount of oxygen to the reaction mixture. While pyrolysis of crude oil is often aided by a catalyst, effective pyrolysis of bio oils requires one.
Wang et al. (2014) demonstrated the poor cracking performance, and investigated the effect of temperature, pressure, additives, and presence of a catalyst on the yield of high-grade hydrocarbon fuels. It was found that the addition of ethanol to the cracking mixture improved yields significantly. Ethanol improves the

Ethanol
At
Overall, while bio-oil derived from algal sources has a lower energy content, due to high oxygen presence in fatty acids, cracking performance is shown to be excellent at lab scale, and strongly resembles current crude oil cracking operations at large scale. While yield by weight is lower, it is still competitive considering the technology discussed is still in its infancy, and has potential for development and industrialisation.
When complete combustion occurs, all hydrocarbon bonds are broken, and reformed into
While the output of an engine can be measured using a dynamo, this gives in incomplete picture of how much combustion is actually occurring. Therefore exhaust gas temperature (EGT) is also measured. A higher exhaust gas temperature generally means that a larger portion of combustion is occurring with optimal stoichiometric ratios. When fuels have similar energy content, exhaust gas temperature can be directly compared to determine which fuel has more desirable combustion characteristics.
(Ge et al., 2022)
Ge et al. (2022) compared the performance of a cooking oil derived bio gasoline created using similar cracking techniques. Studies on the combustion characteristics on algal derived fuels are sparse, but the bio oil the fuels are derived from both contain similar fatty acids, and once pyrolysed, their products are nearly identical in terms of hydrocarbon make up.


(Ge et al., 2022)
It was found that as biogasoline proportion of the fuel increased, both power, and EGT increased in a loosely quadratic manner. At lower concentrations, such as
However once the biogasoline concentration was increased to

(Ge et al., 2022)
It is hypothesised that the biogasoline raised the octane of the fuel, and therefore made less susceptible to premature ignition. This is based on the significantly higher flash point of the fuel. It was also found that the biogasoline had a higher viscosity than regular gasoline. It is thought that the higher viscosity could have lead to insufficient vaporisation, and therefore incomplete or inefficient combustion.
The caloric value of biogasoline was found to be only
A closely related topic is the fuel's burning emissions. As mentioned previously, combustion characteristics differ between fuels. The amount of fuel being burnt daily is tremendous; Transitioning to a fuel with higher emissions will multiply even the smallest difference many times. Further considering the lower energy content of biogasoline, more fuel will be required to release the same amount of energy, therefore higher greenhouse gas (GHG) or nitric oxide (
It should be mentioned that while the carbon released from combustion of biogasoline is derived from the atmosphere and therefore "net zero". Tailpipe emissions of

(Ge et al., 2022)

(Aakko-Saksa et al., 2011)
Considering the previously cited study by Ge et al. (2022), and Aakko-Saksa et al. (2011), a clear trend can be observed.
When percentage of biogasoline
May not be a drop in replacement, as it does not work in cold climates